1. Field of the Invention
The present invention relates to a post for use as a roadside marking post, a traffic sign post, a lamp post, or for other comparable applications in a road traffic environment, and of the kind which is self-raising after having been hit by a vehicle. More specifically, the invention relates to posts of these kind which are made from a channel-shaped plastic profile, the channel-shaped side of which is facing away from the traffic, and which has, at least along its bending zone, a substantially arcuate cross-section.
2. Description of the Prior Art
Self-raising posts of the above kind are known from the U.S. Pat. No. 4,084,914. Posts according to that publication are in the form of a plastic profile which is substantially U-shaped, that is, it consists of two side portions and a flat middle portion therebetween. Unless the angle between the side portions and the middle portion is very obtuse, a bending of a post of this type will cause the material in the side portions to be folded as illustrated in the appended FIG. 1, causing material fatigue which might cause the material to break. It has been suggested, in order to reduce these concentrations of tension in the bending line area of the post, to make the post with an arcuate cross-section. In order to obtain a sufficient strength in the longitudinal direction, this known post is provided, at the channel-shaped innerside, with a reinforcement profile connected to the post by means of rivets or the like.
It has been found that a post of this type will not be self-raising if subjected to a bending of approximately 90.degree., since the upper, bent-around portion of the post is too long and too heavy to allow the springyness of the material to raise the post back up.
Another disadvantage with the known post is that in order for it to resist the stresses it might be subjected to it has to be made from a comparatively expensive plastic material, namely polycarbonate, which has good strength properties but requires a considerable thickness of the material. Furthermore, this material causes great wear on the extrusion moulding tools used for manufacturing the posts.